The present embodiment relates generally to a relative permeability modifying polymer for use with drilling fluids.
While drilling oil and gas wells, a drilling fluid, which may be oil-based or water-based as explained below, is circulated through a drill bit in a well bore and then back to the earth's surface, thereby lubricating the drill string and removing cuttings from the well bore. This phase in the life of a well is known as the “drilling phase.” It is understood that there is also a “production phase” in the life of a well during which hydrocarbons or other desired substances are produced from the well.
The well bore may pass through zones which produce water instead of hydrocarbons. Besides being highly undesirable during the production phase, water producing zones can cause problems in the well bore with certain completion activities. However, water production is generally ignored during the drilling phase.
If the water production problem becomes severe during the production phase, remedial steps such as isolation of the water producing zone and application of a sealant are taken. Obviously, such remedial steps are time consuming and expensive. Moreover, the sealant may interfere with the production of hydrocarbons if it enters a hydrocarbon producing zone.
Recently, wells in the production phase have been successfully treated with compounds known as relative permeability modifiers, which decrease the co-production of water with hydrocarbons by reducing the flow of water through hydrocarbon producing formations, yet have little or no effect on the permeability of the formations with respect to hydrocarbons. However, it is desirable to curb water production as early as possible in the life of a well, and to produce more effective relative permeability modifying compositions.
Thus, what is needed is a method and composition for modifying the permeability of water producing zones during the drilling phase of a well without affecting the subsequent production of hydrocarbons.